(CNN) -- Last month photographs of the discovery of one of the world's last "uncontacted" tribes on the Brazil/Peru border made front covers across the world, vividly illustrating a way of life that is mostly unknown and ignored in the industrialized world.

Indigenous men from different tribes listen to Brazilian President Luiz Inacio Lula da Silva.

But in the group's very "otherness" lies a vulnerability that makes them some of the most marginalized people on Earth.

Far from being a unique example there are actually over 100 tribes across the world -- half of whom live in Brazil and Peru -- that have chosen to reject contact with outsiders and fight for the right to live as their ancestors did before them.

But without proper protection such tribes could soon become extinct, according to Stephen Corry, the director of campaign group Survival International.

"These pictures are further evidence that uncontacted tribes really do exist," he says.

"The world needs to wake up to this, and ensure that their territory is protected in accordance with international law. Otherwise, they will soon be made extinct."

Many remote tribes' refusal to engage with the modern world has meant that they have been forced to effectively live on the run; frequently their communities have been besieged by loggers, mining companies, oil drillers, farmers and cattle ranchers who all want access to the land for themselves.

But it's not only being forced off their land that these groups have to fear, exposure to new diseases for which they have no immunity, can be deadly.

There are cases when half of a tribe has died within the first year of "contact" with the outside world.

Far from bringing "progress" and a better life, contact with the outside world has frequently meant disease, death and drug addiction for tribal people.

Plus, the exposure to a different values system -- that can bring with it drugs, alcohol and prostitution -- can be corrosive to existing social structures leading to the erosion of tribal bonds, depression, suicide, HIV/Aids and obesity.

Jose Carlos dos Reis Meirelles Junior, an official in the Brazilian government's Indian affairs department described the threat to such tribes as "a monumental crime against the natural world" and "further testimony to the complete irrationality with which we, the 'civilized' ones, treat the world".

The struggle to stay detached

The Brazilian government has a policy of not contacting isolated tribes and says it is committed to protecting them.

But human rights activists such as Fiona Watson from Survival International say that the rights of native tribes is still low down on the government's list of priorities, and the small groups of civil servants charged with defending the tribes people find it hard to fight large, high profile projects such as hydro-electric dams that impinge on their lands.

It's a problem by no means limited to South America, and wherever isolated tribes rub up against industrialized society -- from India to Africa, the Americas and Asia -- there is conflict.

Globally the pressure on tribal lands is only increasing as recent hikes in food and oil prices encourage farmers to convert more wild areas to the cultivation of plants for biofuel production, or global commodity crops such as maize, sugar, soy beans and palm oil.

According to Survival International, in Malaysia six million hectares of oil palm have been planted, much of it on indigenous territory, while in Colombia, many indigenous families have been evicted because of palm oil plantations and other crops.

"[Tribal] lands are being increasingly invaded, whether by loggers or settlers or oil companies, and they are facing violence," says Watson.

"So it's absolutely crucial that governments and companies respect and uphold their land rights."

Plus, because the tribes live in such remote areas, it is often hard for police and security services to effectively protect them, even if the Government does make their safety a priority -- a problem that can be compounded by corruption and the collusion of local officials.

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Survival International has recently released shocking video footage of an attack on a Makuxi Indian village in Brazil by men armed with assault rifles and home-made grenades, who they allege were hired by farmers, including the mayor of a nearby town.

Ten people, including six children, were injured in the attack. Although the Makuxi Indians live in an official reserve, ranchers have occupied the land around them illegally and it is claimed they are trying to drive the Makuxi away with threats and violence.

Since the footage was released rancher and local mayor Paulo César Quartiero has been arrested after police found a cache of weapons on his farm.

Freedom to choose progress

In a shrinking world contact between urban society and isolated tribes is becoming increasingly inevitable.

But for Survival International the key objective is to ensure that tribal people are effectively protected by law, giving them the opportunity to control and choose how much contact they would like, if any, giving them the power to direct their own "development."

"It is not that the Yanomami do not want progress, or other things that white people have," said Davi Kopenawa, a shaman from Brazil's Yanomami people.

"They want to be able to choose and not have change thrust upon them, whether they want it or not. "I am not saying I am against progress. I think it is very good when whites come to work amongst the Yanomami to teach reading and writing and to plant and use medicinal plants. This for us is progress.

"What we do not want are the mining companies which destroy the forest and the miners, who bring so many diseases. These whites must respect our Yanomam land. The miners bring guns, alcohol and prostitution and destroy all nature wherever they go. For us this is not progress.